Well, your question is pretty broad but here is what I try to do.
* Severly restrict or eliminate simple carbohydrates like white bread, sugar, juice and processed foods. Instead use whole wheat/grain breads and eat more fruits (the fiber in fruits slows digestion making them a better choice than just juice) and vegetables.
* Good sources of protein include lean meat, fish, poultry, eggs, dairy products and beans. I try to keep my protein at 30% of my calories.
* Don't try to eliminate all the fat from your diet. Fat is necessary for nutrient transfer and nueral function. Try to get your fat from whole food like meat, eggs, dairy, avocados and nuts.
* Stop drinking your calories. Soda and alcoholic drinks have little to no nutritional value. Drink more water.

As you can see although fat is necessary a little goes a long way with more than double the calories per gram than Protein and Carbs. When it comes how much of each to eat you will need to see how your reacts. My split is 30% Protein, 30% Carbs, 40% Fat. (Fitday had a nice chart that will track this for you.) Others have had success with other percentages. I suggest you browse throught the old posts to see what has worked for others.